1. Field of the Invention
The present invention relates to a submerge-type hydraulic elevator control apparatus and, in particular, to a hydraulic elevator control apparatus in which highprecision control is made possible without using a speed detector.
2. Description of the Related Art
For a speed control apparatus of a hydraulic elevator using oil pressure or the like, control systems such as a control system using a flow rate control valve, a pump control system, or a motor revolution control system have been utilized in the past.
Of these, the control system using a flow rate control valve is one in which, while an elevator is moving upward, a motor for sending and receiving pressure oil is rotated at a constant rate to return a fixed quantity of pressure oil discharged from an oil pressure pump to a tank. When a start command is given, the quantity of pressure oil to be returned to the tank is regulated and the speed of the elevator car is controlled, and while the elevator car is moving downward, the downward movement by the self-weight of the elevator car is regulated with a flow rate control valve and the speed is controlled. In this control system, since excess pressure oil is circulated during upward movement and gravitational potential energy is converted to the heat of the pressure oil during downward movement, energy loss is great and the temperature of the pressure oil increases greatly.
In contrast to this, in the pump control system and the motor revolution control system, only a required quantity of pressure oil is sent during upward movement and the above-mentioned enegy loss is suppressed by regenerative braking the motor during downward movement. However, the pump control system is one in which the discharge quantity is controlled using a variable displacement pump and because the structure of its control apparatus and the pump is complex, this system is expensive.
On the other hand, the motor revolution control system is one in which an induction motor is revolution-controlled over a wide range using a variable-voltage variable-frequency (VVVF) inverter. Because a positive displacement type pump is used in this system and its discharge quantity can be controlled by varying the revolution of an induction motor, this system is inexpensive and reliability is high.
FIG. 3 is a configurational view illustrating a conventional hydraulic elevator control apparatus in which a motor revolution control system is used, for example, disclosed in Japanese Patent Laid Open No. 60-248576. FIG. 4 is a side view illustrating the pressure oil driving section within FIG. 3, i.e., the elevator driving section. FIG. 5 is a wiring diagram illustrating the peripheral circuits of an operation instruction contactor which is not shown in FIG. 3. FIG. 6 is a block diagram illustrating the details of the speed control apparatus in FIG. 3. FIG. 7 is a waveform chart illustrating patterns.
In FIG. 3, a cylinder 2 is buried in the pit of an elevator shaft 1 and the cylinder 2 is filled with pressure oil 3. An elevator car 5 is positioned at the top of a plunger 4 supported by the pressure oil 3 via a car floor 6 and a plurality of platform floors 7 are positioned in the side wall of the elevator shaft 1. A cam 8 is disposed on the side outer wall of the elevator car 5 and a plurality of speed reduction instruction switches 9 and stop instruction switches 10 are disposed on the inner wall of the elevator shaft 1 so as to oppose the cam 8.
The pressure oil 3 in the cylinder 2 communicates with an electromagnetic selector valve 11 via a pipe 11a. The electromagnetic selector valve 11 functions as a check valve at all times and when an electromagnetic coil 11b is energized, it conducts in the reverse direction too. An oil pressure pump 12 which communicates with the electromagnetic selector valve 11 via a pipe 12a is rotated in both directions by a three-phase induction motor 13 so as to send and receive the pressure oil 3 between itself and the electromagnetic selector valve 11. The induction motor 13 is provided with, for example, a speed generator 14 for detecting revolution composed of a digital pulse encoder in which photo-couplers or the like are used. The oil pressure pump 12 is provided with a tank 15 for accommodating the pressure oil 3 and the pressure oil 3 is sent and received via a pipe 15a. As shown in FIG. 4, the oil pressure pump 12 is placed on the outside of the tank 15 together with the induction motor 13.
In FIG. 3, an inverter circuit 20 which VVVF-controls the revolution, i.e., the speed, of the induction motor 13 comprises a rectifier 21 which accepts three-phase AC power supplies R, S and T as inputs, a capacitor 22 which smooths a DC voltage from the rectifier 21, an inverter 23 which pulse-width-controls the DC voltage across both ends of the capacitor 22 and which outputs a three-phase AC voltage using VVVF, and an inverter 24 which returns a DC current from the capacitor 22 to the three-phase AC power supplies R, S and T.
Normally open contact points 30a to 30c of an operation contactor 30 (See FIG. 5) are inserted between the induction motor 13 and the inverter circuit 20.
A speed control apparatus 25 for controlling the inverter 23 outputs a control signal 25a on the basis of a speed reduction instruction signal 9a from the speed reduction instruction switches 9, a speed signal 14a from the speed generator 14, an operation instruction signal via the normally open contact point 30Tc of an operation instruction timer relay 30T (See FIG. 5), and an operation signal via a normally open contact point 30d of the operation contactor 30.
In FIG. 5, the operation instruction timer relay 30T, the operation contactor 30, the electromagnetic coil 11b, and a speed control apparatus 25 are each connected in parallel to the (+) and (-) of a control power supply.
A start instruction circuit 28 which is opened by a speed reduction signal 9a and closed by a call signal, a door closure detection signal or the like, is connected in series to the operation instruction timer relay 30T. A series circuit, composed of a normally closed contact point 10b of a stop instruction switch 10 (See FIG. 3) and the normally open contact point 30Ta of the operation instruction timer relay 30T, is connected in parallel to the start instruction circuit 28. Normally open contact points 29a and 29b of an abnormality detection relay (not shown) are connected separately from each other in series to the operation instruction timer relay 30T and the operation contactor 30. The normally open contact points 29a and 29b are usually closed since the abnormality detection relay is in an energized state.
The time-limit-return normally open contact point 30Tb of the operation instruction timer relay 30T is connected in series to the operation contactor 30. A normally open contact point 30f of the operation contactor 30, a normally open contact point 30Td of the operation instruction timer relay 30T, and a downward-movement contact point 41Db which is closed only during downward operation are connected in series to the electromagnetic coil 11b.
In FIG. 6 in which the speed control apparatus 25 is shown in detail, a delay circuit 40 outputs an operation instruction signal delayed by a fixed time via a normally open contact point 30Tc of the operation instruction timer relay 30T. An upward travelling pattern generation circuit 41U and the downward travelling pattern generation circuit 41D each generate predetermined travelling patterns by an operation signal delayed by the delay circuit 40 and switch the travelling pattern to a low speed by the speed reduction instruction signal 9a. An upward-movement contact point 41Ua, which is closed only during upward operation, is connected to the output terminal of the upward travelling pattern generation circuit 41U. A downward-movement contact point 41Da, which is closed only during downward operation, is connected to the output terminal of the downward travelling pattern generation circuit 41D.
A bias pattern generation circuit 45 generates a bias pattern for rotating the oil pressure pump 12 at a number of rotations corresponding to the quantity of the pressure oil 3 leaking from the oil pressure pump 12 at this time according to an operation signal via the normally open contact point 30d of the operation contactor 30 and an operation instruction signal via the normally open contact point 30Tc and sets the bias pattern to zero by the stop instruction signal as the result of the opening of the normally open contact point 30d. An adder 46 adds the bias pattern to either one of the outputs of the travelling pattern generation circuits 41U and 41D.
A conversion circuit 47 makes the level of a speed signal 14a match with the level of travelling patterns. A subtracter 48 calculates the difference between the outputs of the adder 46 and the conversion circuit 47 and inputs the subtraction result to a transmission circuit 49. An adder 50 adds the output of the conversion circuit 47 to the output amplified by the transmission circuit 49 and outputs a frequency command signal .omega.0. A function generator 51 outputs a voltage command signal V which varies linearly with respect to the frequency command signal .omega.0. A reference sine-wave generation circuit 52 outputs a control signal 25a to an inverter 23 on the basis of the frequency command signal .omega.0 and voltage command signal V. The inverter 23 generates a three-phase AC voltage of a sine wave by this control signal 25a.
Shown in FIG. 7 are a bias pattern P1, a travelling pattern P2 during downward movement, a motor pattern P3 corresponding to the number of rotations of the induction motor 13, a car speed pattern P4 of the elevator car 5, and a pressure oil flow rate pattern P5 corresponding to an actual output. A concrete operation of a conventional hydraulic elevator control apparatus shown in FIGS. 3 to 6 will be explained with reference to the waveform charts of these patterns. Since only the polarity differs in the upward and downward travelling patterns, only the travelling pattern P2 during downward movement will be explained.
Suppose that the elevator car 5 is in a stopped state and a call in a downward direction is generated, then a start instruction is input to the elevator car 5 after the door is closed. At this time, the operation instruction timer relay 30T is energized. This energized state is self-held by the closing of the normally open contact point 30Ta and the normally open contact points 30Tb to 30Td are closed.
The closing of the normally open contact point 30Tb causes the operation contactor 30 to be energized and the normally open contact points 30a to 30c of FIG. 3 and the normally open contact point 30f of FIG. 5 are closed. The closing of the normally open contact points 30a to 30c causes the induction motor 13 to be connected to the inverter 23 and is supplied with electricity. The closing of the normally open contact points 30Tc and 30d causes the bias pattern generation circuit 45 of FIG. 6 to generate the bias pattern P1 at time t0, as shown in FIG. 7. This bias pattern P1 causes the inverter 23 to generate a low three-phase voltage of a low frequency and the induction motor 13 drives the oil pressure pump 12 at a low number of rotations corresponding to the quantity of pressure oil leaked from the oil pressure pump 12. Therefore, the elevator car 5 does not move upward by the driving from the bias pattern P1 and remains in a stopped state.
Since the normally open contact points 41Da and 41Db are closed during downward operation, the closing of the normally open contact points 30f, 30Td, and 41Db causes the electromagnetic coil 11b to be energized and the electromagnetic selector valve 11 is opened and becomes fully opened at time tp.
At time t1, after a certain time has elapsed since the normally open contact point 30Tc is closed by the energization of the operation instruction timer relay 30T, the delay circuit 40 generates an output and the downward travelling pattern generation circuit 41D generates the travelling pattern P2 which rises at time t1, as shown in FIG. 7. At this time, the travelling pattern P2 is added to the bias pattern P1 by the adder 46, the induction motor 13 lowers its revolution gradually, as shown in the motor pattern P3, and rotates in a reverse direction from the zero revolution. As a result, the elevator car 5 travels downward, as shown in the car speed pattern P4, and arrives at a constant speed at time t2.
When the elevator car 5 moves downward, and, shortly before it reaches a required position on an object floor, the cam 8 actuates the speed reduction instruction switches 9 to generate a speed reduction instruction signal 9a. As a result, a pattern signal from the downward travelling pattern generation circuit 41D decreases and the elevator car 5 is slowed down at time t3 to a fixed low-speed at time t.sub.4 and continues to move downward. At this time, the start instruction circuit 28 is opened by the speed reduction instruction signal 9a. Therefore, when the cam 8 actuates the stop instruction switch 10 at time t5 and the normally closed contact point 10b is opened, the operation instruction timer relay 30T is de-energized. As a result, since the output from the downward travelling pattern generation circuit 41D falls to zero, the speed of the car further decreases and the elevator car 5 stops at time t6. At this time, even if the operation instruction timer relay 30T is de-energized, the normally open contact point 30Tb makes a time-limit return after the normally open contact point 30Tb is held closed for a fixed time. Therefore, the operation contactor 30 is kept in an energized state and the induction motor 13 continues to be rotated by the bias pattern P1.
On the other hand, the operation instruction timer relay 30T is de-energized by the operation of the stop instruction switch 10 and the normally open contact point 30Td is opened. Therefore, the electromagnetic coil 11b is de-energized and the electromagnetic selector valve 11 is gradually closed and is fully closed at time tD. As a result, the supply of the pressure oil 3 to the tank 15 from the cylinder 2 is stopped and the elevator car 5 is kept in a stopped state.
When the normally open contact point 30Tb is opened at time t7 and the operation contactor 30 is de-energized, the normally open contact points 30a to 30f are opened. As a result, power supply to the induction motor 13 is shut off, the bias pattern generation circuit 45 stops the outputting of the bias pattern P1 and the induction motor 13 stops at time t8.
On the other hand, the operation of the elevator car 5 during upward movement is the reverse of the case where the rotation direction of the induction motor 13 is downward, and is almost the same as the above except that the electromagnetic selector valve 11 is left closed. As described above, the control system using the inverter 23 exhibits excellent performance in a fluid pressure elevator.
In recent years, however, as shown in FIG. 8, for the purpose of further preventing noise and achieving a smaller type, a submerge system, in which an elevator driving section including the oil pressure pump 12 and the induction motor 13 are immersed in the tank 15, has come to be adopted. In this case, since the speed generator 14 as well as the electromagnetic selector valve 11, the oil pressure pump 12 and the induction motor 13 are immersed in the pressure oil 3 in the tank 15, an optical pulse encoder or the like cannot be used for the speed generator 14.
Therefore, for example, as disclosed in Japanese Patent Laid Open No. 64-34881, an arrangement in which only the rotation shaft of the induction motor 13 is made to project outside the tank 15 and the speed generator 14 is placed on the projected portion of the induction motor 13 has been proposed. Actually, however, since the pressure oil 3 flows out of the tank 15 through the rotation shaft of the speed generator 14, this arrangement is also not practical.
As described above, the conventional hydraulic elevator control apparatus has problems in that, since the speed generator 14 is used to control the speed or the induction motor 13, the speed generator 14 must be placed directly in the driving section. This speed generator is of little practical use in a submerge type hydraulic elevator control apparatus and the number of rotations of the induction motor cannot be satisfactorily controlled.